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А не подскажите теорию, или где почитать про связь (в аналитическом виде) между джиттером тактового сигнала, подаваемого на АЦП, и теоретическим SNR АЦП?
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1.ADC Quantisation Noise:The quantisation SNR for an N-bit ADC within a bandwidth BOBS is given by:
SNR (dB) = 6.02N + 1.76 + 10log10(fs / 2BOBS)
Where:
N - Number of bits in ADC
fs - Sample frequency
BOBS - Observation bandwidth
N = 12, fs = 60MHz, BOBS = 1Hz, SNR = 148.77dB
2. ADC Jitter Noise:Jitter within the ADC’s is a combination of several independent
sources of jitter three of which are described below.
z Aperture Jitter
Defined as random fluctuations in the ADCs aperture time about the nominal ADC
aperture time. Adds an amplitude variation or white noise to the sampled signal.
z Clock Jitter
Defined as random fluctuations in the clock period about the nominal clock period.
z Clock distribution systems
These systems can also add further jitter noise into the overall system.
z These sources of jitter within the ADC can be summed to provide an overall jitter
effect. To find the overall ADC jitter we add the variances of the individual jitter
sources.
The Jitter SNR for an ADC with a system jitter level of JRMS digitising a signal of bandwidth BSIG is given by:
SNR (dB) = 20log10(1/(2pBSIGJRMS)
Where:
BSIG - Signal bandwidth
JRMS - RMS jitter level
3. ADC Spurious Free Dynamic Range (SFDR): SFDR is defined as the ratio of the RMS signal amplitude to the RMS value of
the PEAK SPECTRAL COMPONENT (measured over the entire first Nyquist
zone, DC to fSAMPLE/2).
The SFDR therefore considers ALL sources of distortion regardless of their
origin.
For near full scale signals the SFDR is dominated by harmonics of the input
signal.
For signals several dB below full scale other non harmonically related spurs
occur. These spurs are generally due to the differential non-linearity, of the
encoding process, of the ADC itself.
Summary of ADC Effects:Quantisation Noise Constant for an ADC with a fixed resolution.
Independent of sampling frequency. Independent of jitter levels.
Jitter Noise Dependant on rms jitter level.
Increases with undersampling (Decreases with oversampling). Flat across the band.
Spurious Free Dynamic Range - The spurious free dynamic range of any ADC is determined by ALL sources of distortion within the Nyquist band including harmonics of the input signal and the non-linearities within that ADC.
PS.: Взято из
A Discussion of Phase Noise and ADC Limitations on the Dynamic Range of a Multi Channel Radar
